How to Kill an Asteroid

Around 66 million years ago, an asteroid that was perhaps 9 miles wide struck the Earth, an impact that led to the extinction of the dinosaurs.  What if an asteroid that large or even larger was headed toward Earth today?   We've seen this scenario in books and in movies like Armageddon, but I wanted to get some expert input, so I spoke on our podcast, AMSEcast, with Robin Andrews, about his book, How to Kill an Asteroid: The Real Science of Planetary Defense.